1. Field of the Invention
The present invention relates to a high-frequency module that includes a common antenna though which communication signals of different frequency bands can be transmitted and received.
2. Description of the Related Art
In Japanese Unexamined Patent Application Publication No. 2003-152588, a high-frequency module is disclosed that transmits and receives communication signals of different frequency bands using a common antenna. FIG. 1 is a schematic block diagram of the high-frequency module described in Japanese Unexamined Patent Application Publication No. 2003-152588. In FIG. 1, an antenna switch circuit is illustrated.
The high-frequency module described in Japanese Unexamined Patent Application Publication No. 2003-152588 includes a switch SW and a plurality of splitters Dip1 and Dip 2. The switch SW performs switching to connect either of the transmission and reception terminals Tx and Rx of the splitter Dip1 and the transmission and reception terminals Tx and Rx of the splitter Dip2 to an antenna terminal. Thus, communication signals of different frequency bands can be transmitted and received using a single antenna.
Among such high-frequency modules, there are many that are miniaturized since they are to be used in mobile communication terminals for example. As one example of such a situation, there is a high-frequency module in which an internal electrode pattern of a multilayer body and a mount-type circuit device mounted on the multilayer body, for example, a surface acoustic wave duplexer (hereafter, SAW duplexer), are integrated with each other.
However, in a miniaturized high-frequency module, there is a problem in that the gap between the transmission and reception terminals Tx and Rx becomes smaller, interference is more likely to occur between these terminals and the characteristics of isolation of the transmission and reception terminals Tx and Rx from each other are degraded. In addition, since the transmission and reception terminals Tx and Rx utilize the same ground electrode in a multilayer substrate, there is also a problem in that a signal may travel between the transmission terminals Tx and Rx via the ground electrode, thereby degrading the characteristics of isolation of the transmission and reception terminals Tx and Rx from each other.